Invasive fish ta`ape maintains diversity by fast invasion

It seemed to make so much sense back then—if native species aren't doing well, just bring in stronger competitors rather than figuring out why the locals aren't thriving.

(Image: The introduced snapper, Lutjanus kasmira, commonly known as taʻape. Credit: Keoki Stender)

It happened in forestry, bringing in alien trees to reforest the Islands, rather than figuring out why the native forests were ravaged.

And it happened in fisheries, when the Hawai`i Territorial Division of Fish and Game determined, around the time of statehood, to supplement the islands' existing nearshore marine species with three alien reef fishes, Lutjanus fulvus (blacktail snapper or to‘au), Cephalopholis argus (blue-spotted grouper or roi) and Lutjanus kasmira (bluestriped snapper or ta‘ape).

What's been the result? A couple of them have done so well that organizations sponsor targeted fishing tournaments to try to reduce their impact on the reefs and the native species.

A group of scientists from the Hawai`i Institute of Marine Biology has studied the genetics of the three species to learn what happened to them as they settled in to their new Hawaiian home. The researchers are Michelle Gaither, Robert Toonen, and Brian Bowen.

They were released on O`ahu and Hawai`i Islands, but quickly spread to all the Main Hawaiian Islands, and the ta`ape traveled more than 1,000 miles right up the Northwestern Hawaiian Islands chain to Midway Atoll. Roi thus far has made it to French Frigate Shoals. Only to`au remains in the main islands.

The researchers found that the fast-spreading ta`ape maintained its genetic diversity—a diversity similar to that found in the ta`ape of its source islands in Fresh Polynesia. But the slower-spreading species, particularly the to`au, lost much of their genetic diversity.

It suggests that fast growth itself may play a role in protecting diversity of invasive species, they write.

“We now have a better idea of why some species are more successful invaders than others. The faster a species becomes established in its new environment, the faster it finds food and begins to reproduce, the more likely it is to maintain the genetic diversity that is so important to its long term success as an alien species,” said Gaither, in a press release.

For more information the Hawai`i Institute of Marine Biology work in the Northwestern Hawaiian Islands, see www.hawaii.edu/himb/nwhi/. The abstract from their paper in is here: www.ncbi.nlm.nih.gov/pubmed/22874747. The publication is Proc Biol Sci. 2012 Aug 8.

© Jan TenBruggencate 2012